Needles that are actuated at ultrasonic frequencies may be used in various contemporary surgical procedures. For example, the lens of a human eye may develop a cataracteous condition that affects a patient's vision. Cataracteous lenses are sometimes removed and replaced in a procedure commonly referred to as phacoemulsification. Phacoemulsification procedures are typically performed with a hand piece that actuates a needle at ultrasonic frequencies. The needle is inserted through an incision in the cornea up to a desired insertion depth, and then the ultrasonic actuation is used to break the lens within the lens capsule of the eye. The broken lens may be removed through an aspiration line that is coupled to the hand piece, drawing irrigation fluid and aspirated tissue from a hollow passage through the needle.
Phacoemulsification procedures are more likely to be successful if cavitation of the irrigation fluid is limited or controlled to prevent interference with acceptable aspiration. Phacoemulsifacation procedures are also more likely to be successful if heating of tissue at the incision in the cornea, which may be caused by actuation of the needle, is prevented or limited. Therefore, there is a need in the art for an improved apparatus and/or method for ultrasonic actuation of a needle attached to the handpiece of a surgical instrument.